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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Performances orientées système de détecteurs infrarouge à super-réseaux en cryostat opérationnel / Figures of merits at a system level of superlattice infrared Integrated Detector Dewar Cooler Assembly.

Nghiem Xuan, Jean 10 December 2018 (has links)
De nombreuses filières de détecteurs coexistent dans le domaine infrarouge (longueur d’onde entre 1µm et 50µm). Chacune possède ses avantages et ses inconvénients (coût, performance, compacité …). Certaines filières sont bien établies et disponibles commercialement alors que d’autres sont encore émergentes. La filière super-réseaux (SR) est une filière récemment commercialisée. Elle repose sur l’empilement périodique de semiconducteurs (InAs/GaSb), donnant un détecteur quantique capable de détecter des longueurs d’ondes comprises entre 1 et 32µm typiquement.L’objectif de cette thèse est d’évaluer le potentiel de la filière super-réseaux en cryostat opérationnel à l’aide de fonctions de mérite orientées système qui tiennent compte du packaging entourant le détecteur. Nous nous concentrerons sur la Fonction de Transfert de Modulation (FTM), décrivant la résolution du système ainsi que sur le rapport Bruit Spatial Fixe Résiduel sur Bruit Temporel (BSFR/BT), décrivant la stabilité temporelle de la qualité image.Ce travail a ainsi permis de confirmer deux promesses des SR en moyen infrarouge : d’une part, la grande stabilité temporelle de la qualité image et d’autre part le faible nombre de pixels clignotants. Par ailleurs, les bancs de mesures de FTM et de stabilité temporelle développés au cours de la thèse pourront être adaptés pour caractériser d’autres filières dans les mêmes conditions de mesure. / Many photodetector technologies coexist in the infrared domain (wavelength between 1µm and 50µm). Each of them comes with its assets and drawbacks (cost, performance, compactness, etc.). Some technologies are well established and available while others are still under development. The superlattice technology (SL) recently made its way into the market. It is based on the periodic stack of semiconductors (InAs/GaSb), giving a quantum detector capable of detecting wavelengths between 1 and 32µm typically. Like other quantum infrared detectors, superlattice photodetectors need to be cooled at cryogenic temperature to maximize their electro-optical performance.The objective of this thesis is to evaluate the potential of the SLSL in IDDCA using system-oriented figures of merit, which also take into account the packaging of the detector. The present work is focused on the Modulation Transfer Function, which describes the system resolution and the ratio Residual Fixed Pattern Noise over Temporal Noise (RPFN/TN), which evaluates the temporal stability of the image quality.This present work successfully confirmed two promises of the SL in midwave infrared : the excellent stability of the image quality and the low flickering pixel count. Besides, the experimental benches developped (MTF and temporal stability alike) can be adapted to perform similar measurements with other technologies.
2

Automated noise measurements for very long wavelength infrared detectors

Santesmases, David Ramos January 2019 (has links)
The potential imaging performance of infrared (IR) detectors is dependent on the noise level in the detector pixels. Noise measurements at pixel level can therefore provide basic understanding of the intrinsic limitations of detectors. Accurate noise studies with measurements at different biases and with high frequency resolution can however consume a lot of time; therefore, automation of this process is necessary. In this thesis, automation of a noise measurement setup has been implemented. The noise measurement system that has been automated has proven to work for automatically acquiring noise spectra from long wavelength infrared detectors of different types, such as Quantum Well Infrared Photodetectors (QWIPs) and Type II-superlattice (T2SL) detectors. The results of these studies have been used to calculate the noise gain of the detectors. It also has been key to determine discrepancies between different QWIP fabrication batches and helped to clarify the differences in performance of the detectors from those batches. Regarding T2SL, noise measurements on detectors with big differences in dark current have been carried out. Finally, a study of the impact of pixel shape in T2sL noise has been conducted. / Bildkvaliteten hos bildgenererande infraröda (IR) detektorer påverkas av brusnivån i de enskilda pixlarna i detektormatrisen. Brusmätningar på pixelnivå kan därför ge en grundläggande förståelse för vad som begränsar detektorns prestanda. Noggranna studier av bruset, med mätningar vid olika spänningar och med hög frekvensupplösning kan dock vara väldigt tidskrävande, varför automatisering av dessa mätningar är nödvändigt.I detta examensarbete har automatisering av en brusmätuppställning för IR-detektorer utförts.Automatiseringen av brusmätsystemet har fungerat tillfredsställande och har använts för att mäta brus i olika sorters långvågiga IR-detektorer, såsom kvantbrunnsbaserade IR-detektorer (QWIP= Quantum well infrared photodetector) och typ-II supergitterbaserade IR-detektorer (T2SL = Type II superlattice).Resultaten av dessa studier har använts för att beräkna brusförstärkningsfaktorn i dessa detektorer. Studier av brusspektra från olika tillverkningsbatcher av QWIPar har varit en avgörande faktor för att förstå varför detektorprestanda varierar mellan olika batcher. För T2SL-baserade IRdetektorer har studier utförts för att avgöra inverkan av pixelformen, pixelstorlek och mörkerströmsnivå på brusnivån i dessa detektorer.

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